You can hire an appraiser or you can call a real estate agent. The criteria that is used for each varies a bit. Either way, you will get a range, not an exact figure. Keep in mind that your home is only worth what a buyer is willing to pay for it.
A good rule of thumb is to compare it to other homes within 6-12 blocks of your home that are similar. What did they sell for in the past 30-60 days? How does your home compare to theirs using such items as square footage, acreage, age of windows, roof, furnace, AC, water heater and other miscellaneous updates.